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Tool for piercing mill

Active Publication Date: 2015-11-24
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention can increase the lifespan of a tool for a piercing mill and reduce the cost of tools. It can also improve the productivity of high-alloy steel seamless pipes and reduce the production cost. This results in significant industrial benefits.

Problems solved by technology

In the piercing process that uses such a piercing mill, a tool (plug) for a piercing mill is exposed to a high-temperature and high-load environment for a long time and wear, erosion, and the like are easily caused.
The technologies described in Patent Literatures 1, 2, 3, 4, and 5 pose a problem in that, when such a high-alloy steel is pierced, a tool is quickly worn.

Method used

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Examples

Experimental program
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Effect test

examples

[0068]A molten steel having the composition shown in Table 1 was melted in a high-frequency furnace with an air atmosphere and cast by a V process (vacuum sealed molding, process) to obtain a piercer plug having a maximum outer diameter of 174 mmφ. The obtained piercer plug was used as a substrate steel. The substrate steel was subjected to a heat treatment (A), (B), or (C) shown in FIG. 3 to obtain a tool for a piercing mill that includes a scale layer and a microstructure on the substrate steel side below the interface. Table 2 shows the obtained tool for a piercing mill. The tool for a piercing mill was used in piercing.

[0069]The heat treatment (A) included a first-stage heat treatment and a second-stage heat treatment. In the first-stage heat treatment, the substrate steel was held at a heating temperature of 920° C. for 4 hours and then cooled t 700° C. at a cooling rate of 40° C. / h. In the second-stage heat treatment, the substrate steel was held at a heating temperature of 92...

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Abstract

A tool for a piercing mill, the tool comprising a scale layer in a surface layer of a substrate steel, wherein the scale layer includes a net structure scale layer that is formed on a substrate steel side, has a thickness of 10 to 200 μm in a depth direction, and is complicatedly intertwined with a metal; and wherein a microstructure on the substrate steel side in a range of at least 300 μm in the depth direction from an interface between the net structure scale layer and the substrate steel contains a ferrite phase at an area fraction of 50% or more, the ferrite phase containing 400 / mm2 or more ferrite grains having a maximum length of 1 to 60 μm.

Description

TECHNICAL FIELD[0001]The present invention relates to the production of a seamless pipe and particularly to the improvement in wear resistance of a tool for a piercing mill such as a plug used for piercing.BACKGROUND ART[0002]A Mannesmann piercing method has been widely known as a method for producing a seamless pipe. In this method, first, a material to be pierced (round billet) that is heated to a certain temperature is subjected to a piercing process with a piercing mill to obtain a hollow shell. Subsequently, the wall thickness is decreased by using an elongating mill such as an elongator, a plug mill, or a mandrel mill. Furthermore, reheating is performed when necessary and then the outer diameter is mainly decreased with a stretch reducing mill or a sizing mill to obtain a seamless pipe having a predetermined size.[0003]Examples of a known piercing mill include a Mannesmann piercer in which a pair of inclined rolls, a piercing plug, and two guide shoes are combined; a three ro...

Claims

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Application Information

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IPC IPC(8): C22C38/44C22C38/60C22C38/00C21D9/00B21B25/00C21D9/22C22C38/52C22C38/48C22C38/02C21D1/84C22C38/06C22C38/04B21B25/04
CPCC22C38/52B21B25/00C21D1/84C21D9/00C21D9/22C22C38/00C22C38/002C22C38/02C22C38/04C22C38/06C22C38/44C22C38/48C22C38/60B21B25/04C21D2211/005Y10T428/24967
Inventor ICHINO, KENJIOZAKI, SEIJIMOCHIDA, TETSUO
Owner JFE STEEL CORP
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